Learning about exposure can take some time. It may seem overwhelming, but once it sinks in it becomes second nature. And just a bit of clarification - what you see in the view finder is the Exposure Indicator. The +/- button on the camera is for Exposure Compensation. When you hold that button down and scroll the thumb wheel you override the camera's exposure to either increase or decrease the exposure. As others have suggested, you may need to do that at times because your camera's idea of a correct exposure can be wrong.

Remember that the camera does not know what any given scene or subject is. All it 'sees' is rectangular frame with various levels of brightness, and it assumes that if you combine all those values it should average out to a middle toned exposure. This is nothing more than cold hearted math, an algorithm that does calculations on the fly. It is often very good, but it has no soul. It does not appreciate the golden glow of a sunset, or the twinkle in the eye of your beloved child. All it sees are brightness values. You as the photographer must take over to get the results you are looking for.

I suggest that you start by setting your camera to Aperture Priority. This takes advantage of the camera's meter, but also lets you override it as needed. You set the aperture based on the subject, and the camera takes care of the shutter speed. If you want a shallow depth of field (portrait, wildlife, action) you open the aperture to f/4 or whatever your widest setting is. If you want more depth of field (landscape, group shot, architecture) you close the aperture as needed - usually in the f/8 to f/16 range. As you change the aperture, the camera will adjust the shutter speed accordingly. If you take a shot and it's under or over exposed, then use the EC button to adjust. If the shutter gets too slow for sharp images then just bump the ISO up.